Two varieties of pyrite from the Basal Reef of the Witwatersrand system

Abstract

Compared to isotropic pyrite, anisotropic pyrite contains much higher trace arsenic, nickel, and cobalt, has slightly lower reflectivity, and is not as hard. Pyrite is not a reliable standard for reflectivity and other types of measurement when trace-element content is unknown. Since the two types are intergrown, it is clear that cobalt and nickel values do not have genetic implications.